netdev - Re: e100 + VLANs?

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Message-ID: <4E96ADD3.90100@msgid.tls.msk.ru>
Date:	Thu, 13 Oct 2011 13:22:27 +0400
From:	Michael Tokarev <mjt@....msk.ru>
To:	Jesse Brandeburg <jesse.brandeburg@...el.com>
CC:	David Lamparter <equinox@...c24.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: e100 + VLANs?

On 12.10.2011 03:38, Jesse Brandeburg wrote:
[..]
>> The knowledge and code for this is actually around line 1142 of e100.c:
>>         if (nic->mac >= mac_82558_D101_A4) {
>>                 config->fc_disable = 0x1;       /* 1=Tx fc off, 0=Tx fc on */
>>                 config->mwi_enable = 0x1;       /* 1=enable, 0=disable */
>>                 config->standard_tcb = 0x0;     /* 1=standard, 0=extended */
>>                 config->rx_long_ok = 0x1;       /* 1=VLANs ok, 0=standard */
>>
>> where rx_long_ok is the configuration bit to enable frame reception
>> for >1514 byte frames. I guess your card is < mac_82558_D101_A4...
>>
>> (cf. "Intel 8255x 10/100 Mbps Ethernet Controller Family Open Source
>> Software Developer Manual" page 78/86 - "Long Receive OK. This bit is
>> reserved on the 82557 and should be set to 0. When this bit is set on
>> the 82558 or 82559, the device considers received frames that have
>> a data field longer than 1500 bytes as good frames.")
> 
> David, thank you for posting that, while you were typing I was
> researching the same thing, so FWIW, I concur with your conclusion.
> 
> ouch, OP your hardware is really really old:
>> 00:12.0 Ethernet controller: Intel Corporation 82557/8/9/0/1 Ethernet Pro 100 (rev 02)
>> Subsystem: Intel Corporation EtherExpress PRO/100B (TX)
> 
> rev 2 is D100_C, which is 82557.
> 
> the hardware is NOT capable of long receives (i.e. vlan packets).
> If it was then they should generally fit in the receive buffer and be
> handled and not discarded.

Can this knowlege be added to the driver somehow, so that others
will not hit the same trap as I did? :)  _If_ there's any value
in that (I guess there aren't many users with that hardware left),
and if that's easy to do ofcourse... ;)

Thanks!

/mjt
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